1. Field of the Invention
The present invention relates generally to a method and a device for transferring data and information enabling an estimate of the wireless link between a source and a receiver using single carrier orthogonal frequency division multiplex scheme.
2. Description of Related Art
Single carrier orthogonal frequency division multiplex modulation scheme is a modulation scheme with orthogonal frequency division multiplex type multiplexing but single-carrier-like envelope. It can be implemented either in the time-domain or in the frequency-domain and is also called discrete Fourier transform spread orthogonal frequency division multiplex.
The main advantage with respect to orthogonal frequency division multiplex is that the discrete Fourier transform pre-coding restores the single carrier nature of the signal, i.e. a low peak to average power ratio.
Pilot sequences transmission is necessary for enabling the determination of an estimate of the wireless link between a source and a receiver. It is commonly considered that a pilot sequence cannot be scattered with single carrier orthogonal frequency division multiplex modulation scheme data without completely degrading the peak to average power ratio structure of the transmitted signal.
That's the reason why, in 3GPP TSG-RAN, “TR 25.814: “Physical Layer Aspects for Evolved UTRA”, Version 7.1.0, 2006-09, pilot sequence is mapped on all the subcarriers, referenced as a pilot symbol. Such a pilot symbol is regularly inserted in the frame. In this case, a classical way of performing channel estimation is to estimate the channel at the pilot symbols positions and finally the channel is estimated at all positions by performing a time interpolation between two pilot symbols.
The drawback of this classical method appeared in the time interpolation. In order not to reduce the data throughput too much, one must limit the number of inserted pilot symbols. For example, if the pilot insertion rate is 1/12, it implies that a pilot symbol shall be inserted every twelve orthogonal frequency division multiplex symbols. This limits the capability of the system to follow the channel variations of the signal for example due to the Doppler effect.
According to the Nyquist theorem, if the orthogonal frequency division multiplex rate is 1/Ts, a bound on the maximum acceptable Doppler frequency is equal to:
      f          m      ⁢                          ⁢      ax        =      1          24      ⁢              T        s            